Method of making magnetic alloys



Patented My 3, 1927.

PATENT OFFICE.

VERE .B. BROWNE, OI BRAGKENBIDGE, PENNSYLVANIA.

. METHOD OF MAKING MAGNETIC ALLOYS.

No Drawing.

This invention relates to magnetic alloys and more-particularly to a method of producing high grade silicon iron for use as a magnetic alloy.

The value of silicon iron for this use depends in alarge measure upon the soundness of the metal, the silicon content thereof, the carbon content and the temperature at which the ingots are-cast. By soundness of the metal, I mean its freedom from slag and'other solid inclusions such as silica.

It is highly important that the ingots be cast at a certain temperature and this, under the present methods of manufacture is difficult because of the exothermic reaction that occurs when siliconand iron combine in the ladle to form silicides.

It is also highly important to have as little variation as possible in the silicon content 'from that specified. Under the present methods of production, the silicon content of a silicon iron alloy containing over 2% of silicon varies considerably and sometimes this variation exceeds .5%. The present method of manufacture consists in adding .the total quantity of silicon desired either to the ladle or to the furnace when the heat is ready to tap and the ordinary errors in weight. loss of metal and over-oxidation of the bath all contribute to produce this variation.

The true degree of'variation is often not indicatedby the analysis for the reason that in the ordinary methods of analysis, the

silica present in the steel will be determined and reported as silicon and for this reason,

it is highly important to remove as much silica as possible before the metal is cast into ingots.

An object of this invention is to provide a commercial method of producing magnetic alloys such as silicon iron or so-called silicon steel by the practice of which I am enabled to obtain a product that is substantially free from slag and other solid inclusions such as-silica. 1

A further object, is to provide a method of producing'such alloys-by means of which the silicon content can be controlled so as not to vary more than from 1% to 2% from I that specified.

A still further object is to provide a method whereby the temperature at which'the ingots are cast can be controlled within narrow limits.

. Application filed March 19, 1925. Serial No. 16,837.

These, as well as other objects which will appear to those skilled in the art of making silicon iron or silicon steel alloys, I attain by means of the method disclosed and claimed herein.

In practicing my invention I employ a reservoir or receiver capable of holding a relatively large amount of metal in the form of a molten bath. The reservoir (container) 1s heated, and means are provided for slightly agitating the bath or setting up circulatory currents therein of such character as to assist in the elimination of the slag and other foreign solids.

The form and size of the reservoir is unimportant, so also is the type of fuel used in heating the same. This may be as or oil. but I-prefer to heat the bath electrically.

Slight agitation or circulation within the bath may be' accomplished by suitably gyratinglorwobbl'ing the container and advantage may be'taken of the natural laws f relating to the circulation of liquids if the heat is properly applied. 1

The slight circulation necessary to assist in the flotation of the foreign solids to the surface of the bath can be obtained by applying external heat to a segregated portion of the bath in such manner that the molten metal thus heated will slowly flow into the body of the bath and will be replaced by relatively colder metal flowing from the 7 body into the segregated portion. By suitably controlling the heat applied to this segregated portion, moderate circulatory currents may be set up and the bath thereby agitated to the desired extent.

An electric heater of the induction type admirably adaptsitself as a combined heater and agitator. Instead of applyin heatcontinuously'to the segregated portlon of the 1 bath this portion may he heated intermittently and in this way the bath'will be in-/ termittently agitated. Such a procedure will assist the slag and other solid inclusions which occur in the form of an emulsion-to float to the surface 'of the bath and combine with the slag on the surface. I i If the bath is kept molten and at substantially pouring temperature, the sla and other foreign solids, if given time, to the surface withoutagitation, but slight agitation, however, (either constant or m termittent) will ordinarily. assist in this flotation. u

' but little external or directly to the reservoir.

The reservoir or container must, of'course, be lined with some suitable refractory and it will preferably be provided with atap ping spout so located that any predetermined amount of metal at a time may be withdrawn.

naces into a ladle and the silicon is then added in the ladle. This metal is then transferred to the reservoir.

In carrying out the method of this invention, the reservoir after being heated to the desired temperature, is filled with molten metal. The amount of silicon added may be such that the metal in the reservoir approximates the composition desired in the finished alloy. I prefer, however, to keep the silicon content a little below that desired in the finished material Under certain circumstances, it may be found desirable to charge the reservoir with pure refined iron and to make the silicon addition in the reservoir instead of in the ladle. If from time to time, it is found by analysis that the silicon content of the molten metal in the reservoir is lower than that desired, additional silicon may be added If desired, however, the next charge from the preparation furnace may be given an excessive addition of silicon suflieient to make up the deficiency in the reservoir.

After the reservoir has once been filled with molten alloy, the cycleofoperationof my process consists broadly in tapping at more or less re lar intervals definite amounts of metal rom the reservoir and in replenishing the bath in the reservoir with molten alloy in amounts substantially equal to those withdrawn.

By maintaining the silicon content of the bath slightly below that desired in the fin- .ished alloy, the silicon content of the ingots can be controlled within very narrow limits, for when a ladleful of purified alloy is tapped from the reservoir it is'only necessary to add enough-silicon to bring the silicon content to that specified.

The bath within the reservoir is preferably maintained at pouring temperature, and, since the molten metal which is periodically charged into the reservoir is brought to a relatively high temperature by the exothermic reaction that occurs when the silicon is added to the metal in the ladle,

additional heat is required to maintain the bath at pouring temperature.

By maintaining the relatively lar e bath at pouring temperature and with rawing therefrom from time to time relatively small amounts which are replaced by like small amounts, the slag and other solid inclusions such as silica even though the bath is not agitated float to-thesurface and combine with the slag on the surface. Slight agitation, however, ordinarily assists in this flotation.

In starting the cycle. of operation under this invention, the bath is maintained intact, that is, no metal is tapped therefrom until suflicient time has elapsed to insure the removal of all of the slag and other solid in clusions. The charges for replenishing the bath from time to time are relatively so small as compared with the total bath that the amount of slag and other solid inclusions in each replenishing charge will only slightly contaminate the bath. The time between withdrawals must be sufiicient for this slight amount of slag and other solid inclusions to float to the surface and combine with the slag.

I maintain on the surface of the bath a specially .prepared slag of such composition that the slag and other foreign solids will combine therewith. The composition of this prepared'slag may be varied as desired, but I prefer to use a slag of calcium silicate "dissolved in caleium'oxide, since such a slag will remain in equilibrium with the bath and will remove a considerable amount of sulphur.

After the reservoir is initially fully charged with molten alloy and sufficient, time has elapsed for the metal to reach the state a ladleful of the purified alloy. This is usu-.

ally cast into ingots then rolled into sheet bars and then into sheets under regular methods. i

A ladleful of metal is then tapped from one of the preparation furnaces and after adding to this the desired amount of silicon, it is poured into the reservoir.

The silicon is preferably added in the form'of ferro-silicon and this is preferably heated and placed in the ladle before the molten metal is tapped thereinto.

No further Il'lOtilllS withdrawn from the reservoir until another heat is ready to be tapped from one of the preparation furnaces.

of the bath in the reservoir is 3.5% and it is desired to obtain 3.75% in the ingot,- I add to the ladle suflicient silicon to make up this additional If it is found that the silicon content is 4%, I add a quantity of pure iron to the ladle suflicient to reduce the siliconkcontent the necessary amount.

This pure iron addition-may either be in solid or molten form.

I find as I have said.- that under most circumst-ances, it is desirable to keep the silicon content of the bath below that desired in the -finished product, for by the addition of silicon to the ladle "in quantities sufficient to make up slight deficiencies, I am enabled to obtain extremely accurate control of the siliconcontent of the ingot.

By means "of this method of controlling the silicon content I am enabled to obtainfinished material that does not vary more than from 1% to 2% from that specified.

Under some circumstances, it is desirable to maintain a concentrated bath in the reservoir, that is, one that contains more silicon than is desired in the finished product, and, when the process is practiced in this way,

I I add to the ladle pure molten iron from one of the preparation furnaces in suflicient quantity to dilute the concentrated alloy the necessary amount.

I find that sheets rolled from alloy produced by my. method are uniformly high grade both as to the soundness of the metal and as ,to the silicon content.

In my co-pending application, Serial No. 16,838, I have disclosed a method of producing silicon iron having a carbon content of notover 03% and I prefer totiise the method of said application in preparing the refined iron for use in the present method, since it is preferable to have the carbon content of the finished product as low as pos sible.

' It will be understoodthat in producing other alloys beside silicon iron or so-called silicon steel, the method disclosed herein may be advantageou ly practiced especially where the soundness o the alloy, that is, its

freedom from slag an other solid inclusions such as s1h'ca 1s importance.

Havlng thus described 1y invention, what I I claim is:

LThe method of making silicon iron substantially free from solid inclusions and having a definite siliconcontent, which con-- sists in collectin and storing within a contamer a relative y large bath of such alloy and applying external heat to the same, in

holding the stored metal within the-container until substantially all of the solid set up therein and in tapping metal from the bath substantially free from silica.

3. The method of making silicon iron free from silica and other solid inclusions except in negligible amounts.which consists in collecting and storing within a container a relatively large bath of silicon iron, in maintaining the bath at substantially pouring temperature for a sufficient length of time to allow the emulsified silica and other solid inclusions to float to the surface of the bath, in from time to time tapping relatively small amounts of metal from the bath, inreplenishing the bath with molten alloy of substantially the same analysis and in subst'antially the same amounts as that tapped and in casting the same into ingots.

4. The method of making sound silicon iron having a definite silicon content. which consists in collecting and storing within a container a relatively large bath of molten silicon iron in which the silicon content is slightly below that required in the finished material, in maintaining the bath intact for a sufficient length of time to allow the silica and other solid inclusions to float to the surface of the bath and in assisting such flotation by causing circulatory currents to be set up within the bath, in from time to time tapping relatively small amounts of metal from the bath, in repleni hing the bath with molten alloy of substantially the same analysis and in substantially the same amounts as that tapped, in adding to the tapped metal sufficient silicon to bring the analysis thereof 'to that desired in the finin replenishing the bath after each tapping with molten silicon iron in substantially the same amount as that tapped therefrom.

6. The method of making silicon iron substantially free from solid inclusions which consists in collecting and storing within a container a relatively large bath of the same, in agitating the bath and maintaining it at pouring temperature by applying heat from an external source to a segregated but connected portion of the bath and in from time to time tapping relatively small amounts of metal from the bath and then in replenishing the bath.

7. The method of making silicon iron substantially free from solid inclusions except in negligible amounts, which consists in collecting and storing within a container a relatively large bath of such alloy in maintaining the bath at substantially pouring temperature by applying, heat from an ex" ternal source to a segregated but connected portion of the bath, in from time to time tapping relatively small amountsof alloy from the bath, in replenishingthe bath with molten alloy of substantially the same analysis and insubstantially; the same amounts as that tapped and in casting the tapped alloy into ingots.

8. The method of making silicon iron substantially free from solid inclusions, which consists in collecting and storing within a container a relatively large bath of silicon iron, in applying heat from an external source to a segregated but connected portion of the bath whereby the bath by convection t is maintained at pouring temperature and flotation of the solid inclusions is fac'ilitated, in from time to time tapping relatively small amounts of metal from the bath and after each tapping in replenishing the bath with substantially the same amount of molten silicon iron as that tapped therefrom.

9. The'method of making ingots of silicon iron free from silica and other solid incl'usions except in negligible amounts, which consists in' collecting and storing within a container a relatively large bath of silicon iron, in maintaining the bath at substant ally pouring temperature by applying heat Irom an external source to a segregated but connected portion of the bath, in from time to time tapping relatively small amounts of metal from the bath, in replenishing the bath with molten silicon iron of substantially the same analysis and in substantially the same amounts as that tapped and in casting the tapped metal into ingots.

gated but connected portion of the bath, in from time to time tapping relatively small amounts of metal and in replenishing the bath thereafter.

In testimony whereof, I have hereunto sub 'cribed my name this Mthday of March,

i VER-E B. BROWN E. 

